Apparatus for use in dispensing paper towel, personal care products and the like are often provided in public restrooms, commercial food preparation areas and similar settings in order to assist patrons and employees in maintaining personal hygiene. These dispensers are typically provided to supply the user with a product such as a sheet of paper towel. A lever, push bar or other device is commonly provided to actuate the dispenser. Product is dispensed when the user grasps and pulls the lever or presses her hand against the push bar or other actuator. These dispensers have proven to be reliable and cost effective and are completely satisfactory for their intended purpose.
In certain applications there has been a recent trend toward the use of automatic dispenser apparatus in place of, or in addition to, manually-operated dispensers. In theory, automatic dispensers operate by dispensing the towel in response to the proximity of the user and without contact between the user and the dispenser device. The dispenser detects the presence of the user (typically the user's hand) adjacent the dispenser housing and automatically discharges the towel in response to a signal generated by detection of the user.
It can be appreciated that there are benefits potentially associated with automatic dispenser apparatus. For example, automatic dispensers may limit the transfer of germs or other agents to the user's hand because the user is, in theory, not required to physically contact the dispenser device. The appearance and cleanliness of the dispenser may be enhanced through reduced physical contact between the dispenser and the user. This not only improves the appearance of the dispenser but has related benefits in terms of reducing the effort required to maintain the dispenser. Yet another potential benefit is that the dispenser may be more effective in controlling or limiting the amount of product dispensed from the device thereby providing uniform amounts of dispensed product and reducing waste.
Efforts have been made to develop automatic dispenser apparatus which utilize proximity sensors of various types to detect the presence of the user and to dispense in response to the presence of the user. One approach has been to utilize photoelectric dispensers of various types. Examples include U.S. Pat. No. 6,069,354 (Alfano et al.) and U.S. Pat. No. 4,786,005 (Hoffman et al.). For example, the dispenser apparatus of Alfano and Hoffman utilize reflectance-type infrared detection systems to actuate the dispenser. The user places his hand adjacent a localized infrared light generator and changes in light reflectance are detected by a photo transistor to generate a signal actuating the dispenser. Hoffman includes a further photo transistor detector provided to detect changes in ambient light resulting from the presence of the user's hand.
The generator and detector of Alfano are localized at a specific position on the front side of the dispenser while in the Hoffman dispenser these elements are located in a cavity formed in the dispenser housing where ambient light conditions can be controlled. None of these detection components are positioned at the location where the towel is dispensed, i.e., the position where the user's hand would naturally be expected to extend. As a result, these dispensers may not be ergonomic for all users. Further, such photoelectric-based systems may not operate properly in conditions of potentially variable ambient light, such as in a public restroom. Other examples of automatic dispensers utilizing photoelectric sensor devices include U.S. Pat. No. 6,293,486 (Byrd et al.), U.S. Pat. No. 6,105,898 (Byrd et al.) and U.S. Pat. No. 5,772,291 (Byrd et al.), U.S. Pat. No. 5,452,832 (Niada) U.S. Pat. No. 4,796,825 (Hawkins), U.S. Pat. No. 4,722,372 (Hoffman et al.) and U.S. Pat. No. 4,666,099 (Hoffman et al.).
Another approach has been to utilize detected changes in an electrical field as a means to actuate the dispenser. Examples include U.S. Pat. No. 6,279,777 (Goodin et al.), U.S. Pat. No. 5,694,653 (Harald), U.S. Pat. No. 4,921,131 (Binderbauer), U.S. Pat. No. 4,826,262 (Hartman et al.), U.S. Pat. No. 6,412,655 (Stützel et al.) and Canadian Patent Application Serial No. 2,294,820 (Stützel et al.).
For example, Hartman discloses an automatic cloth towel dispenser which dispenses clean cloth towel and takes up the soiled towel following use. Hartman utilizes a detection device which consists of a bulky, elongated coil which oscillates to generate a radio frequency field below the dispenser cabinet. The oscillator circuit is said to detect small changes in the RF field. Hartman requires unduly large components and may be prone to detection of false signals. Furthermore, such a system would likely be adversely affected by conditions of high humidity which are commonly encountered in environments where the dispenser might be expected to be located.
By way of further example, the dispenser apparatus of the Stützel patent describes what is called a capacitive sensor which includes a flat, two-dimensional pair of electrodes with very specific electrode surface area ratios and placement requirements. The electrodes are said to generate a rectified field. The patent asserts that placement of an object within 1.18″ of the dispenser will produce changes in capacitance which, when detected, are used to actuate the dispenser. Such a system is disadvantageous at least because the range of detection is limited and the location of the field is not ergonomic. The user is required to be extremely close to the dispenser, potentially resulting in unwanted contact between the user and the dispenser apparatus.
The dispenser of the Goodin patent requires a “theremin” antenna which is said to detect changes in capacitance as the user's hand approaches the dispenser. In response, a solenoid is actuated to dispense liquid soap. To eliminate the risk of false detection, a second sensor may be provided to independently detect the presence of the user's hand. The need for primary and secondary sensors suggests that the system is not entirely reliable.
There is also a need to provide improved control over dispenser operation which compensates for changes in battery voltage which occur over the life cycle of the batteries used to power the dispenser. Improved control is useful to ensure that the length of sheet material dispensed is consistent in each dispense cycle even as battery voltage decreases as the batteries become discharged. This need for improved dispenser control exists for all types of battery powered dispensers including for hands-free dispensers with a proximity detector input device and for dispensers which utilize an input device such as a contact switch to initiate a dispense cycle.
It would be a significant improvement in the art to provide automatic dispenser apparatus with an improved proximity sensor wherein the proximity sensor would positively detect the presence of a user without physical contact by the user and dispense in response to the detection, which would operate in an ergonomic manner by detecting the user at a range and position from the dispenser along which the user would be expected to place his or her hand or other body part, which would discriminate between signals unrelated to the presence of the user, which would be compact permitting use in small dispenser apparatus and avoiding interference with the operation of other dispenser components, which would operate reliably under a wide range of ambient light, humidity and temperature conditions which could include certain other optional features provided to enhance the operation of the dispenser and which would include an improved control apparatus.